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hybrid_udp.coffee
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hybrid_udp.coffee
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# Hybrid UDP
# - can send fire-and-forget (unreliable) packet
# - can send reliable packet which requires ACK
###
# Usage
hybrid_udp = require './hybrid_udp'
server = new hybrid_udp.UDPServer
server.on 'packet', (buf, addr, port) ->
# buf is a Buffer instance
console.log "server received: 0x#{buf.toString 'hex'}"
if buf[0] is 0x04
# shutdown server
server.stop()
console.log "server stopped"
server.start 9999, "localhost", ->
console.log "server started"
client = new hybrid_udp.UDPClient
client.start 9999, "localhost", ->
console.log "client started"
console.log "client: writing 0x010203"
client.write new Buffer([0x01, 0x02, 0x03]), ->
console.log "client: writing 0x040506 and waiting for ACK"
client.writeReliable new Buffer([0x04, 0x05, 0x06]), ->
console.log "client: received ACK"
client.stop()
console.log "client stopped"
###
events = require 'events'
dgram = require 'dgram'
logger = require './logger'
MAX_PACKET_ID = 255
FRAGMENT_HEADER_LEN = 2
RESEND_TIMEOUT = 100 # ms
PACKET_TYPE_UNRELIABLE = 0x01
PACKET_TYPE_REQUIRE_ACK = 0x02
PACKET_TYPE_ACK = 0x03
PACKET_TYPE_RESET = 0x04
OLD_UDP_PACKET_TIME_THRESHOLD = 1000
RECEIVE_PACKET_ID_WINDOW = 10
INITIAL_PACKET_ID = 0
zeropad = (width, num) ->
num += ''
while num.length < width
num = '0' + num
return num
exports.UDPClient = class UDPClient
constructor: ->
@pendingPackets = []
@newPacketId = 0
@maxPacketSize = 8000 # good for LAN?
# @maxPacketSize = 1472 # good for internet
@isInBlockMode = false
@ackCallbacks = {}
@serverPort = null
@serverHost = null
@isStopped = false
@socket = dgram.createSocket 'udp4'
@socket.on 'error', (err) ->
logger.error "UDPServer socket error: #{err}"
@socket.close()
@socket.on 'message', (msg, rinfo) =>
@onMessage msg, rinfo
start: (serverPort, serverHost, callback) ->
@serverPort = serverPort
@serverHost = serverHost
# bind to any available port
@socket.bind 0, '0.0.0.0', =>
@resetPacketId callback
stop: ->
@isStopped = true
@socket.close()
onMessage: (msg, rinfo) ->
packetType = msg[0]
if packetType is PACKET_TYPE_ACK
packetId = msg[1]
if @ackCallbacks[packetId]?
@ackCallbacks[packetId]()
else
logger.warn "ACK is already processed for packetId #{packetId}"
else
logger.warn "unknown packet type: #{packetType} len=#{msg.length}"
logger.warn msg
getNextPacketId: ->
id = @newPacketId
if ++@newPacketId > MAX_PACKET_ID
@newPacketId = 0
return id
sendPacket: (packetType, packetId, buf, callback) ->
sendData = new Buffer @maxPacketSize
sendData[0] = packetType
sendData[1] = packetId
fragmentSize = @maxPacketSize - FRAGMENT_HEADER_LEN - 2
if fragmentSize <= 0
throw new Error "maxPacketSize must be > #{FRAGMENT_HEADER_LEN + 2}"
bufLen = buf.length
totalFragments = Math.ceil bufLen / fragmentSize
# maximum number of fragments is 256
if totalFragments > 256
throw new Error "too many fragments: #{totalFragments} (buf.length=#{bufLen} / fragmentSize=#{fragmentSize})"
endFragmentNumber = totalFragments - 1
sendData[2] = endFragmentNumber
fragmentNumber = 0
wroteLen = 0
sentCount = 0
sendNextFragment = =>
if wroteLen >= bufLen
throw new Error "wroteLen (#{wroteLen}) > bufLen (#{bufLen})"
remainingLen = bufLen - wroteLen
if remainingLen < fragmentSize
thisLen = remainingLen
else
thisLen = fragmentSize
sendData[3] = fragmentNumber
buf.copy sendData, 4, wroteLen, wroteLen + thisLen
fragmentNumber++
@socket.send sendData, 0, thisLen + 4, @serverPort, @serverHost, =>
wroteLen += thisLen
sentCount++
if sentCount is totalFragments
callback?()
else
sendNextFragment()
sendNextFragment()
resetPacketId: (callback) ->
buf = new Buffer [
# packet type
PACKET_TYPE_RESET,
# packet id
INITIAL_PACKET_ID,
]
@newPacketId = INITIAL_PACKET_ID + 1
isACKReceived = false
# wait until receives ack
@waitForACK INITIAL_PACKET_ID, ->
isACKReceived = true
callback?()
# send
@socket.send buf, 0, buf.length, @serverPort, @serverHost
setTimeout =>
if not isACKReceived and not @isStopped
logger.warn "resend reset (no ACK received)"
@resetPacketId callback
, RESEND_TIMEOUT
rawSend: (buf, offset, length, callback) ->
@socket.send buf, offset, length, @serverPort, @serverAddress, callback
write: (buf, callback) ->
if @isInBlockMode
@pendingPackets.push [@write, arguments...]
return
packetId = @getNextPacketId()
@sendPacket PACKET_TYPE_UNRELIABLE, packetId, buf, callback
_writeReliableBypassBlock: (buf, packetId, onSuccessCallback, onTimeoutCallback) ->
isACKReceived = false
# wait until receives ack
@waitForACK packetId, ->
isACKReceived = true
onSuccessCallback?()
# send
@sendPacket PACKET_TYPE_REQUIRE_ACK, packetId, buf
setTimeout =>
if not isACKReceived and not @isStopped
logger.warn "resend #{packetId} (no ACK received)"
onTimeoutCallback()
, RESEND_TIMEOUT
_writeReliable: (buf, packetId, callback) ->
if @isInBlockMode
@pendingPackets.push [@_writeReliable, arguments...]
# TODO: limit maximum number of pending packets
return
@_writeReliableBypassBlock buf, packetId, callback, =>
@_writeReliable buf, packetId, callback
writeReliable: (buf, callback) ->
packetId = @getNextPacketId()
@_writeReliable buf, packetId, callback
waitForACK: (packetId, callback) ->
@ackCallbacks[packetId] = =>
delete @ackCallbacks[packetId]
callback?()
flushPendingPackets: (callback) ->
if @pendingPackets.length is 0
callback?()
return
packet = @pendingPackets.shift()
func = packet[0]
args = packet[1..]
origCallback = args[func.length-1]
args[func.length-1] = =>
@flushPendingPackets callback
origCallback?()
func.apply this, args
_writeReliableBlocked: (buf, packetId, callback) ->
@_writeReliableBypassBlock buf, packetId, callback, =>
@_writeReliableBlocked buf, packetId, callback
# Defer other packets until this packet is received
writeReliableBlocked: (buf, callback) ->
if @isInBlockMode
@pendingPackets.push [@writeReliableBlocked, arguments...]
return
@isInBlockMode = true
packetId = @getNextPacketId()
@_writeReliableBlocked buf, packetId, =>
@isInBlockMode = false
@flushPendingPackets callback
fragment: (buf, fragmentSize=maxPacketSize) ->
fragments = []
remainingLen = buf.length
while remainingLen > 0
if remainingLen < fragmentSize
thisLen = remainingLen
else
thisLen = fragmentSize
fragments.push buf[0...thisLen]
buf = buf[thisLen..]
return fragments
exports.UDPServer = class UDPServer extends events.EventEmitter
constructor: ->
super()
@socket = dgram.createSocket 'udp4'
@socket.on 'error', (err) ->
logger.error "UDPServer socket error: #{err}"
@socket.close()
@socket.on 'message', (msg, rinfo) =>
@onReceiveMessage msg, rinfo
@isStopped = false
@resetServerState()
resetServerState: ->
@videoReceiveBuf = {}
@processedPacketId = null
@latestPacketId = null
@bufferedPackets = {}
@packetLastReceiveTime = {}
onReceiveMessage: (msg, rinfo) ->
packetType = msg[0]
packetId = msg[1]
endFragmentNumber = msg[2]
fragmentNumber = msg[3]
if packetType is PACKET_TYPE_RESET
@resetServerState()
@latestPacketId = packetId
@processedPacketId = packetId
@sendAck packetId, rinfo.port, rinfo.address
return
@packetLastReceiveTime[packetId] = Date.now()
if @latestPacketId?
if (packetId <= @latestPacketId + RECEIVE_PACKET_ID_WINDOW and
packetId > @latestPacketId) or
packetId < @latestPacketId - 50
@latestPacketId = packetId
else
@latestPacketId = packetId
if endFragmentNumber > 0 # fragmentation
if @videoReceiveBuf[packetId]?
# check if existing packet is too old
if Date.now() - @videoReceiveBuf[packetId].time >= OLD_UDP_PACKET_TIME_THRESHOLD
logger.warn "drop stale buffer of packetId #{packetId}"
@videoReceiveBuf[packetId] = null
if not @videoReceiveBuf[packetId]?
@videoReceiveBuf[packetId] =
buf: []
totalReceivedLength: 0
targetBuf = @videoReceiveBuf[packetId]
targetBuf.buf[fragmentNumber] = msg[4..]
targetBuf.time = Date.now()
targetBuf.totalReceivedLength += msg.length - 4
isMissing = false
for i in [0..endFragmentNumber]
if not targetBuf.buf[i]?
isMissing = true
break
if not isMissing # received all fragments
try
receivedBuf = Buffer.concat targetBuf.buf
@onReceivePacket
packetType: packetType
packetId: packetId
port: rinfo.port
address: rinfo.address
body: receivedBuf
catch e
logger.error "concat/receive error for packetId=#{packetId}: #{e}"
logger.error e.stack
logger.error targetBuf.buf
finally
delete @videoReceiveBuf[packetId]
delete @packetLastReceiveTime[packetId]
else # no fragmentation
receivedBuf = msg[4..]
delete @videoReceiveBuf[packetId]
delete @packetLastReceiveTime[packetId]
@onReceivePacket
packetType: packetType
packetId: packetId
port: rinfo.port
address: rinfo.address
body: receivedBuf
consumeBufferedPacketsFrom: (packetId) ->
oldEnoughTime = Date.now() - OLD_UDP_PACKET_TIME_THRESHOLD
loop
if not @bufferedPackets[packetId]?
break
if @packetLastReceiveTime[packetId] <= oldEnoughTime
logger.warn "packet #{packetId} is too old"
break
@onCompletePacket @bufferedPackets[packetId]
delete @bufferedPackets[packetId]
@processedPacketId = packetId
if packetId is MAX_PACKET_ID
packetId = 0
else
packetId++
return
deleteOldBufferedPackets: ->
if @processedPacketId is @latestPacketId
return
isDoneSomething = false
if @processedPacketId is MAX_PACKET_ID
oldestUnprocessedPacketId = 0
else
oldestUnprocessedPacketId = @processedPacketId + 1
oldEnoughTime = Date.now() - OLD_UDP_PACKET_TIME_THRESHOLD
for packetId in [oldestUnprocessedPacketId...@latestPacketId]
if not @packetLastReceiveTime[packetId]?
@packetLastReceiveTime[packetId] = Date.now()
if @packetLastReceiveTime[packetId] <= oldEnoughTime
# Failed to receive a packet
timeDiff = oldEnoughTime - @packetLastReceiveTime[packetId]
logger.warn "dropped packet #{packetId}: #{timeDiff} ms late"
isDoneSomething = true
if @bufferedPackets[packetId]?
delete @bufferedPackets[packetId]
if @processedPacketId is MAX_PACKET_ID
@processedPacketId = 0
else
@processedPacketId++
else
break
if isDoneSomething
if @processedPacketId is MAX_PACKET_ID
nextPacketId = 0
else
nextPacketId = @processedPacketId + 1
@consumeBufferedPacketsFrom nextPacketId
return
onReceivePacket: (packet) ->
anticipatingPacketId = @processedPacketId + 1
if anticipatingPacketId is MAX_PACKET_ID + 1
anticipatingPacketId = 0
if packet.packetId is anticipatingPacketId # continuous
@processedPacketId = packet.packetId
@onCompletePacket packet
if packet.packetId is MAX_PACKET_ID
nextPacketId = 0
else
nextPacketId = packet.packetId + 1
@consumeBufferedPacketsFrom nextPacketId
else # non-continuous
if @processedPacketId - RECEIVE_PACKET_ID_WINDOW <= packet.packetId <= @processedPacketId
logger.warn "duplicated packet #{packet.packetId}"
if packet.packetType is PACKET_TYPE_REQUIRE_ACK
@sendAck packet.packetId, packet.port, packet.address
return
@bufferedPackets[packet.packetId] = packet
@deleteOldBufferedPackets()
onCompletePacket: (packet) ->
if packet.packetType is PACKET_TYPE_REQUIRE_ACK
@sendAck packet.packetId, packet.port, packet.address
setTimeout =>
@emit 'packet', packet.body, packet.address, packet.port
, 0
sendAck: (packetId, port, address, callback) ->
buf = new Buffer [
# packet type
PACKET_TYPE_ACK,
# packet id
packetId
]
@socket.send buf, 0, buf.length, port, address, callback
start: (port, address, callback) ->
@socket.bind port, address, callback
stop: ->
@isStopped = true
@socket.close()